In a manufacturing process of a semiconductor apparatus having a three-dimensional memory cell structure, a laminated film including an oxide film, a silicon nitride film, and the like is formed on a well and thereafter a concave portion having a high aspect ratio, such as a slit or a via hole, is formed in the laminated film to reach the well. The aspect ratio is the ratio of a width and a depth of the concave portion, that is, a value obtained by dividing the depth by the width. Ions as impurities are then implanted by an ion implantation apparatus into the well located on the bottom of the concave portion, so that an impurity diffusion layer is formed. In the formation of the diffusion layer, an implantation amount (dose) of ions is measured with a Faraday cup. When an accumulated amount of the implantation amount has reached a predetermined amount, ion implantation is terminated.
When an aspect ratio is high, the range of an implantation angle of ions within which ions can reach the bottom of the concave portion is narrower than when the aspect ratio is low. The implantation angle is determined by a tilt angle that is an inclination of a surface normal of a wafer with respect to a beam axis (a center) of an ion beam, beam-axis deviation that is deviation of the beam axis from the center of the wafer, a beam angular dispersion that is dispersion of the ion beam from the beam axis (a divergence angle), and the like.
Because of the narrow range of the implantation angle within which ions can reach the bottom of the concave portion, the accuracy of the implantation angle largely affects the measurement accuracy of the Faraday cup when the aspect ratio is high. Specifically, in a case where the accuracy of the implantation angle is poor, an implantation amount of ions actually implanted to the bottom of the concave portion is not accurately reflected on the implantation amount measured with the Faraday cup. In this case, a semiconductor apparatus having a diffusion layer formed based on a measurement result of the Faraday cup may not exhibit a desired performance.
Therefore, it is required to accurately measure an implantation amount of ions implanted to the bottom of the concave portion in order to manufacture a semiconductor apparatus having a concave portion with a high aspect ratio with a stable yield.